Traditional bi-level light fixture systems involve the use of a single illuminant that is controlled with Infrared or ultrasonic sensors to reduce the flux output from a high level during occupancy to a predefined reduced level during periods of vacancy. This control technology is typically applied to single or multiple sources of the same spectrum or color temperature characteristic.
There is a growing concern that certain light levels at night may result in biological disturbance or imbalances within certain species due to the hormonal stimulation that occurs with shorter wavelengths corresponding to typical high color temperature light sources. For example, there is growing evidence from the vision science community indicating adverse impacts on humans associated with wavelengths shorter than 500 nanometers (nm) that occur from lighting at night. Studies have shown that human circadian rhythm is mediated by photoreceptors within the eye with a peak response near 450 nm, i.e., typically the blue portion of the visible light spectrum. Exposure to blue light within this critical action spectrum shorter than 500 nm can suppress the normal production of melatonin, a critical hormone that mediates sleep function and other physical responses.
The total amount of light flux entering the sky and disrupting natural wildlife in areas adjacent to the parking and area lighting complexes can have a disruptive effect on wildlife in a similar manner to what is currently being studied with humans.